My PC suddenly started getting slow for no reason

What could it be? I have 16 GB of RAM, a Ryzen 5600. Out of nowhere the PC started getting slow, but only for some things, like opening certain programs, opening a single YouTube video…

The strange thing is that this had never happened before. My Windows and all programs are installed on an NVMe SSD with a speed of 7 GB/s if I’m not mistaken. And I still have plenty of free space.

RAM usage stays between 35 and 40% when I check with Ctrl + Alt + Del, so I believe there’s still a lot of headroom.

CPU temperature doesn’t even reach 50 degrees, not even when I’m playing something, it doesn’t go much higher than that. I don’t know what else to test. Maybe 16 GB of DDR4 RAM is no longer enough to open simple programs?

In games, I don’t have any stuttering at all and I don’t get low FPS or anything like that.